True round pre-emptive multi-tasking for one. Windows 3.1 used cooperative multi-tasking which means the applications themselves were responsible form checking the message queue to see if another app wanted CPU. Windows didn't have true multi-tasking until Windows 95.

Anyone who trusts scientists has no idea how science works. You don't trust the person or title, you trust the chain of independent verification of the data. This is a critical thinking issue.